Showing papers by "Chang Jung Kim published in 2012"

Gated three-terminal device architecture to eliminate persistent photoconductivity in oxide semiconductor photosensor arrays

Abstract: The composition of amorphous oxide semiconductors, which are well known for their optical transparency, can be tailored to enhance their absorption and induce photoconductivity for irradiation with green, and shorter wavelength light. In principle, amorphous oxide semiconductor-based thin-film photoconductors could hence be applied as photosensors. However, their photoconductivity persists for hours after illumination has been removed, which severely degrades the response time and the frame rate of oxide-based sensor arrays. We have solved the problem of persistent photoconductivity (PPC) by developing a gated amorphous oxide semiconductor photo thin-film transistor (photo-TFT) that can provide direct control over the position of the Fermi level in the active layer. Applying a short-duration (10 ns) voltage pulse to these devices induces electron accumulation and accelerates their recombination with ionized oxygen vacancy sites, which are thought to cause PPC. We have integrated these photo-TFTs in a transparent active-matrix photosensor array that can be operated at high frame rates and that has potential applications in contact-free interactive displays.

Multi-level switching of triple-layered TaOx RRAM with excellent reliability for storage class memory

Abstract: A highly reliable RRAM with multi-level cell (MLC) characteristics were fabricated using a triple-layer structure (base layer/oxygen exchange layer/barrier layer) for the storage class memory applications. A reproducible multi-level switching behaviour was successfully observed, and simulated by the modulated Schottky barrier model. Morevoer, a new programming algorithm was developed for more reliable and uniform MLC operation. As a result, more than 107 cycles of switching endurance and 10 years of data retention at 85°C for all the 2 bit/cell operation were archieved.

High performance bilayer oxide transistor for gate driver circuitry implemented on power electronic devices

Abstract: The integration of electronically active oxide transistors onto silicon circuits represents an innovative approach to improving the performance of devices. In this paper, we present high performance oxide transistor for use as gate drive circuitry integrated on top of a power electronic device, providing a novel power system. Specifically, as a core device component in gate driver, oxide transistor exhibits remarkable performance such as, high mobility (23∼47cm2/Vs) and high breakdown voltage (BV) of 60∼340V despite low process temperatures (<300°C). In addition, we demonstrate the dynamic behavior of the inverter and the latch produced by oxide transistor and thus a complete and functioning gate drive circuitry can be implemented on top of power management integrated circuit (PMIC) as depicted in the report.

The Effects of Gadolinium Incorporation Into Indium–Zinc–Oxide Thin-Film Transistors

Abstract: We investigated the effects of gadolinium (Gd) incorporation into indium-zinc-oxide (IZO) thin-film transistors (TFTs) using radio-frequency cosputtering of IZO and Gd. A gadolinium-indium-zinc-oxide (Gd-IZO) TFT with 2.4 at.% Gd content had saturation-mode field-effect mobility, threshold voltage, and switching ratio (on current/off current) of 6.6 cm2V-1s-1, 1.04 V, and on the order of 107, respectively, after thermal annealing at 250 °C. A Gd-IZO TFT with 2.4 at.% Gd content showed better switching performance and thermal stability than pure IZO TFTs due to stable ionic bond between Gd and O.

Low-Temperature Fabrication and Characteristics of Lanthanum Indium Zinc Oxide Thin-Film Transistors

Abstract: We fabricated lanthanum indium zinc oxide (IZO) (La-IZO) thin-film transistors (TFTs) using radio frequency cosputtering of IZO and lanthanum. The field-effect mobility and switching ratio of the La-IZO TFTs were 4.2 cm2·V-1·s-1 and on the order of 108, respectively, before thermal annealing and 3.02 cm2·V-1·s-1 and on the order of 1010, respectively, after thermal annealing at 150°C in air. Our La-IZO TFTs had better thermal stability than pure-IZO TFTs due to the stable ionic bond between La and O.